https://www.bbc.com/news/world-asia-33755182.amp
After holding a discussion with the President, Mr Stimson wrote in his diary on 24 July 1945 that "he was particularly emphatic in agreeing with my suggestion that if elimination was not done, the bitterness which would be caused by such a wanton act might make it impossible during the long post-war period to reconcile the Japanese to us in that area rather than to the Russians".
Tensions that led to the Cold War were already brewing and the last thing the Americans wanted to do was bolster the Communist cause in Asia.
That was when Nagasaki was added to the target list instead of Kyoto. But Hiroshima and Nagasaki were not military targets either.
As we know today, hundreds of thousands of civilians, including women and children, were killed. And while Kyoto may have been the most famous cultural city, the other cities also had valuable assets.